The Server Message Block protocol has a venerable history rooted in the early days of IBM PC LANs and it is getting an update in Longhorn Server. Ward Ralston explains at the Windows Server Division WebLog:
We have listened to our customers on the limitations that were present with the original SMB protocol and have removed the restrictive constants in the protocol so we never need to worry about the protocol itself being the limiting factor for scalability. This includes increasing the number of concurrent open file handles on the server, the number of shares that a server can share out amongst other key enhacements which include:
- SMB2 will have transaction support, i.e. full two-phase commit transactional semantics are available over the new SMB protocol. This takes advantage of the new Transactional File System (TxF) feature in NTFS in Longhorn Server
- Client Side Encryption. This allows over the wire encryption of data, i.e. a file is encrypted on the client and sent out to the server where previously the file would have been sent in the clear over the wire and encrypted on the server
- Support for symbolic links over the new protocol
- Supports an arbitrary extensible way of compounding operations to reduce round trips. This is what will primarily enable less chattiness which has often been a major pain point
- The new protocol supports larger buffer sizes than previously allowed
All of this sounds great, but I would be remiss if I didn’t mention that the SMB protocol and Microsoft proprietary extensions to it played an important part in the various antitrust trials and there will undoubtedly be similar scrutiny of SMB2.